This invention relates to electrically conductive barium sulfate-containing compositions, to the use of the electrically conductive compositions, and to a process of producing them.
In some applications of plastics, their electrical insulating propoerties give rise to technical problems. The electrical insulating properties of plastics are particularly undesirable, for instance, when electronic components must be shielded from relatively large electromanetic fields, such as is the case with commuter housings, or when electric charges are to be discharged from components. The electrical insulating properties of plastics result in difficulties when high explosives or IC components are to be kept in storage, and in the manufacture of medical rubber articles or carpeting provided with an antistatic finish or in the production of electrically conductive adhesives for metal. It is known that polymers can be rendered electrically conductive by an addition of conductive particles. Such conductive particles may consist of metal or carbon black particles as well as of particles made of semiconducting oxides, such as zinc oxide, or iodides, such as copper iodide. A disadvantage involved in the use of metal or carbon black particles is that the polymers containing the additives have a black color, which is not desired in numerous cases. The use of particles of zinc oxide results in undesired temperature-dependent fluctuations of the electrical conductivity. Because polymers which contain copper iodide have only a low chemical stability, they can be used only for a limited number of applications.
JP-56157438-A describes a process of producing a powder mixture which can be added to plastics in order to render them electrically conductive. In that process a solution which contains SnCl.sub.4 and SbCl.sub.3 is added to an aqueous dispersion of barium sulfate which has been heated. A precipitation is effected in an acid medium and results in mixed powders consisting of SnO.sub.2 powder and BaSO.sub.4 powder. But the plastics to which the mixed powders have been added have an electrical conductivity which is thermally unstable. Besides, the mixed powders have a relatively poor dispersibility in plastics so that problems arise in the production of a homogeneous mixture consisting of the mixed powders and plastics.